Vanadium-containing petroleum fuels modified with manganese and alkali metal additives



Oct. 9, 1962 A. G. ROCCHlNl ETAL 3,057,152

VANADIUM-CONTAINING PETROLEUM FUELS MODIFIED WITH MANGANESE AND ALKALI METAL ADDITIVES Filed June 14, 1960 2 Sheets-Sheet l E i i E u E "Q 'n z N v Q N x? z w R "a E w 3 uwwroxs RLBERT G. ROCCHIN/ By Cl/HRLES E. TRHUTHHN ATTOQIVEY Oct. 9, 1962 ROCCHINI ETAL 3,057,152 VANADIUM-CONTAINING PETROLEUM FUELS MODIFIED WITH MANGANESE AND ALKALI METAL ADDITIVES 2 Sheets-Sheet 2 Filed. June 14, 1960 OON OOm

'Nl 'OSl'SW NI SSO'I 1M NOISOHHOO INVENTORS. ALBERT G. ROCCHINI BYCHARLES E. TRAUTMAN United States Patent Ofifice 3,057,152 Patented Oct. 9, 1962 3,057,152 VANADlUlV-CONTAENING PETRULEUM FUELS MfiDiFlED WTTH MANGANESE AND ALKALI METAL ADDKTEVES Albert G. Rocclrini, @alrmont, and Charles E. Trautman,

Qizeswiclr, Pm, assignors to Gulf Research a Development ilornpany, Pittsburgh, Pa, a corporation of Dela= ware Filed Tune 14, 1060, fier. No. 36,@% 7 Claims. (Cl. 60-39.t}2)

This invention relates to vanadium-containing petroleum fuels. More particularly, it is concerned with rendering non-corrosive those residual fuels which contain such an amount of vanadium as normally to yield a corrosive vanadium-containing ash upon combustion.

This application is a continuation-in-part of our prior copending application, Serial No. 701,844, filed December 10, 1957, now abandoned, and assigned to the same assignee as the present application.

It has been observed that when a residual type fuel oil containing substantial amounts of vanadium is burned in furnaces, boilers and gas turbines, the ash resulting from combustion of the fuel oil is highly corrosive to materials of construction at elevated temperatures and attacks such parts as boiler tubes, hangers, turbine blades, and the like. These effects are particularly noticeable in gas turbines. Large gas turbines shOW promise of becoming an important type of industrial prime mover. However, economic considerations based on the efiiciency of the gas turbine dictate the use of a fuel for this purpose which is cheaper than a distillate diesel fuel; otherwise, other forms of power such as diesel engines become competitive with gas turbines.

One of the main problems arising in the use of residual fuel oils in gas turbines is the corrosiveness induced by those residual fuels containing sufficient amounts of vanadium to cause corrosion. Where no vanadium is present or the amount of vanadium is small, no appreciable corrosion is encountered. While many residual fuel oils as normally obtained in the refinery contain so little vanadium, or none, as to present no corrosion problems, such non-corrosive fuel oils are not always avail-able at the point where the oil is to be used. In such instance, the cost of transportation of the non-corrosive oil to the point of use is often prohibitive, and the residual oil loses its competitive advantage. These factors appear to militate against the extensive use of residual fuel oils for gas turbines. Aside from corrosion, the formation of deposits upon the burning of a residual fuel in a gas turbine may result in unbalance of the turbine blades, clogging of openings and reduced thermal efficiency of the turbine.

Substantially identical problems are encountered when using a solid residual petroleum fuel containing substantial amounts of vanadium. These fuels are petroleum residues obtained by known methods of petroleum refining such as deep vacuum reduction of asphaltic crudes to obtain solid residues, visbreaking of liquid distillation bottoms followed by distillation to obtain solid residues, coking of liquid distillation bottoms, and the like. The solid residues thus obtained are known variously as petroleum pitches or cokes and find use as fuels. Since the vanadium content of the original crude oil tends to concentrate in the residual fractions, and since the processing of the residual fractions to solid residues results in further concentration of the vanadium in the solid residues, the vanadium corrosion problem tends to be intensified in using the solid residues as fuel.

The vanadium-containing ash present in the hot flue gas obtained from the burning of a residual fuel containing substantial amounts of vanadium compounds causes catastrophic corrosion of the turbine blades and other metal parts in a gas turbine. The corrosive nature of the ash appears to be due to its vanadium oxide content. Certain inorganic compounds of vanadium, such as vanadium oxide (V 0 which are formed on combustion of a residual fuel oil containing vanadium compounds, vigorously attack various metals, their alloys, and other materials at the elevated temperatures encountered in the combustion gases, the rate of attack becoming progressively more severe as the temperature is increased. The vanadium-containing ash forms deposits on the parts affected and corrosively reacts with them. It is a hard, adherent material when cooled to ordinary temperatures.

It has already been proposed to employ in corrosive residual fuels small amounts of certain metal compounds to mitigate the vanadium corrosion. Such compounds are of varying effectiveness and it has not always been possible to reduce vanadium induced corrosion to a minimum amount.

It has now been found that residual petroleum fuels containing vanadium in an amount sufficient to yield a corrosive vanadium-containing ash upon combustion can be rendered substantially non-corrosive by incorporating therein, to form a uniform blend, an amount of a vanadium-free manganese compound sufficient to yield from about 0.5 to 3 atom weights of manganese per atom weight of vanadium in said fuel, and an amount of a vanadium-free alkali metal compound sufficient to yield from about 0.5 to 3 atom weights of alkali metal per atom weight of vanadium in said fuel, the total amount of manganese and alkali metal being at least about 1 atom Weight but not exceeding about 4 atom weights per atom Weight of vanadium. In the fuel compositions of the invention the coaction of the two additive components is such that the corrosion is reduced to negligible amounts.

In the accompanying drawings, the FIGURE 1 shows an apparatus for testing the corrosivity of residual fuel oil compositions, and FIGURE 2 shows in graphic form the individual effects and combined elfects of certain of the described additives in retarding corrosion.

The type of residual fuel oils to which the invention is directed is exemplified by No. 5, No. 6 and Bunker C fuel oils which contain a sufiicient amount of vanadiurn to form a corrosive ash upon combustion. These are residual type fuel oils obtained from petroleum by methods known to the art. For example, residual fuel oils are obtained as liquid residua by the conventional distillation of total crudes, by atmospheric and vacuum reduction of total crudes, by the thermal cracking of topped crudes, by visbreaking heavy petroleum residua, and other conventional treatments of heavy petroleum oils. Residua thus obtained are sometimes diluted with distillate fuel oil stocks, known as cutter stocks, and the invention also includes residual fuel oils so obtained,

provided that such oils contain suflicient vanadium normally to exhibit the corrosion characteristics described herein. It should be understood that distillate fuel oils themselves contain either no vanadium or such small amounts as to present no problem of corrosion. The total ash from commercial residual fuel oils usually ranges from about 0.02 to 0.2 percent by weight. The vanadium pentoxide (V content of such ashes ranges from zero to trace amounts up to about 5 percent by weight for low vanadium stocks, exhibiting no significant vanadium corrosion problem, to as much as 85 percent by Weight for some of the high vanadium stocks, exhibiting severe corrosion.

The type of vanadium-containing solid residual fuels to which the invention is directed is exemplified by the coke obtained in known manner by the delayed thermal coking or fluidized coking of topped or reduced crude oils and by the pitches obtained in known manner by the deep vacuum reduction of asphaltic crudes to obtain solid residues. These materials have ash contents of the order of 0.18 percent by Weight, more or less, and contain corrosive amounts of vanadium when prepared from stocks containing substantial amounts of vanadium. A typical pitch exhibiting corrosive characteristics upon combustion had a softening point of 347 F. and a vanadium content, as vanadium, of 578 parts per million.

In accordance with the invention, any manganese compound, organic or inorganic, which is free from vanadium is used as the manganese component additive. Similarly, any organic or inorganic vanadium-free alkali metal compound is employed to furnish the alkali metal component. The alkali metal compounds of the invention include sodium, potassium, lithium, rubidium and cesium compounds. Because of their low cost and suitability for the purposes of the invention, sodium and potassium compounds are preferred.

Examples of inorganic compounds suitable for use in accordance with the invention :are the alkali metal and manganese oxides, hydroxides, acetates, carbonates, oxalates, sulfates, nitrates, halides, and the like. In this connection, the mixture of salts present in sea water, as disclosed in our copending application, Serial No. 654,812, filed April 24, 1957, now U.S. Patent 2,966,029, comprises a suitable alkali metal compound.

The organic compounds of manganese and the alkali metals include the oil-soluble and oil-dispersible salts of acidic organic compounds such as: 1) the fatty acids, e.g., valeric, caproic, Z-ethylhexanoic, oleic, palmitic, stearic, linoleic, tall oil, and the like; (2) alkylaryl sulfonic acids, e.g., oil-soluble petroleum sulfonic acids and dodecylbenzene sulfonic acid; (3) long chain alkyl sulfuric acids, e.g., lauryl sulfuric acid; (4) petroleum naphthenic acids; (5) rosin and hydrogenated rosin; (6) alkyl phenols, e.g., iso-octyl phenol, t-ibutylphenol, and the like; (7) alkyl phenol sulfides, e.g., bis(iso-octyl phenol)monosulfide, bis(t-butylphenol)disulfide, and the like; (8) the acids obtained by the oxidation of petroleum waxes and other petroleum fractions; and (9) oil-soluble phenolformaldehy-de resins, e.g., the Amberols, such as t-butylphenol-formaldehyde resin, and the like. Since the salts or soaps of such acidic organic compounds as the fatty acids, naphthenic acids and rosins are relatively inexpensive and easily prepared, these are preferred materials for the organic additives.

When employing in residual fuels the inorganic additives of the invention, it is desirable to use finely-divided materials. However, the degree of subdivision is not critical. One requirement for using a finely-divided material is based upon the desirability of forming a fairly stable dispersion or suspension of the additives when blended with a residual fuel oil. Furthermore, the more finelydivided materials are more efiicient in forming uniform blends and rendering non-corrosive the relatively small amounts of vanadium in a residual fuel, whether the fuel be solid or liquid. The inorganic additives are therefore employed in a particle size range of less than 250 microns, preferably less than 50 microns. However, Where the inorganic additives are Water-soluble, for example, in the case of manganese nitrate, sodium carbonate, and the like, it is unnecessary to employ finelydivided materials since, if desired, the additives can be dissolved in water to form a more or less concentrated solution and the water solution emulsified in the fuel.

The organic additives of the invention are oil-soluble or oil-dispersible and are therefore readily blended with residual fuels to form uniform blends. Since on a weight basis in relation to the fuel, the amounts of the additives are small, it is desirable to prepare concentrated solutions or dispersions of the organic additives in a naphtha, kerosene or gas oil for convenience in compounding.

In the practice of the invention with vanadium-containing residual fuel oils, the mixture of additives is uniformly blended with the oil in the disclosed proportions. This is accomplished by suspending the finely-divided dry additives in the oil, by emulsifying or dispersing a concentrated water solution of the water-soluble inorganic additives in the oil, or dissolving or dispersing the organic additives in the oil. If desired, suitable surface active agents, such as sorbitan mo-noolea-te and monolaurate and the ethylene oxide condensation products thereof, glycerol monooleate, and the like, which promote the stability of the suspensions or emulsions can be employed.

In the practice of the invention with the solid residual fuels, incorporation of the additives of the invention is accomplished in several ways. The additives can be suspended, emulsified or dissolved in the liquid vanadiumcontaining residual stocks or crude oil stocks from which the solid residual fuels of the invention are derived, and the mixture can then be subjected to the refining process which will produce the solid fuel. For example, in the production of a pitch by the deep vacuum reduction of an asphaltic crude oil, the additives or a concentrate thereof are slurried with the oil in proportion to the vanadium content thereof, and the whole subject to deep vacuum reduction to obtain a pitch containing the additives uniformly dispersed therein. As still another alternative, particularly with a pitch which is withdrawn in molten form from the processing vessel, the additives can be mixed with the molten pitch and the mixture allowed to solidify after which it is ground to the desired size.

In the case of either liquid or solid residual fuels, the additives can be separately fed into the burner as concentrated solutions or dispersions. In such a case, it is preferred to meter the additives into the fuel line just prior to the combustion zone. In a gas turbine plant where the heat resisting metallic parts are exposed to hot combustion gases at temperatures of the order of 1200 F. and above, the additives can be added separately from the fuel either prior to or during combustion itself, or even subsequent to combustion. However they may specifically be added, whether in admixture with or separately from the fuel, the additives are introduced into said plant upstream of the heat resisting metal parts to be protected from corrosion.

It is a characteristic feature of the invention that the use of both the manganese and alkali metal additives in the proportions described and claimed results in an unexpectedly greater reduction in corrosion to lower, substantially minimal amounts than can be obtained by using either the manganese or alkali metal additives singly in the same total additive content. This unexpected coaction is obtained when the amount of manganese additive is in the range of about 0.5 to 3 atom weights of manganese per atom weight of vanadium in the fuel and the amount of alkali metal additive is also in the range of about 0.5 to 3 atom Weights of alkali metal per atom weight of vanadium, the total amount of additive, however, being in the range of about 1 to 4 atom weights of additive metals per atom Weight of vanadium. When the total additive content is less than about 1 atom weight corrosion rises rapidly, and when the total additive content is greater than about 4 atom weights the reduction in corrosion tends to approach the reduction in corrosion obtained with the same total amount of the manganese additive used alone.

The following specific examples are further illustrative of the invention. In these examples, the sodium naphthenate and manganese naphthenate are salts of petroleum naphthenic acids and are employed as solutions in petroleum naphtha. The sodium naphthenate contains 6 percent by weight of sodium and the manganese naphthenate contains 6 percent by weight of manganese.

EXAMPLE I With a residual fuel oil uniformly blend 0.9 percent by weight of the above manganese naphthenate solution and 0.11 percent by weight of the above sodium naphthenate solution. The residual fuel oil employed has the following inspection:

Gravity: API 21.4 Viscosity, Furol: Sec.:

122 F. 21.5 Flash, 00: F. 175 Fire, OC: F. 195 Sulfur, B: percent 1.6 Ash: percent 0.04 Vanadium, P.p.m. of oil 166 Sodium, P.p.m. of oil 3 The resulting composition has an atom weight ratio of manganese to vanadium of 3:1 and an atom weight ratio of sodium to vanadium of 1:1.

EXAMPLE II Uniformly blend with a residual fuel oil 0.88 percent by weight of the above manganese naphthenate solution and 0.184 percent by weight of the above sodium naphthenate solution. The residual fuel oil employed has the The resulting composition has an atom weight ratio of manganese to vanadium of 2:1 and an atom weight ratio of sodium to vanadium of 1:1.

EXAMPLE III To the same residual fuel oil of Example II add and uniformly blend 0.22 percent by weight of the above manganese naphthenate solution and 0.092 percent by weight of the above sodum naphthenate solution. The resulting composition has an atom weight ratio of manganese to vanadium of 0.5:1 and an atom weight ratio of sodium to vanadium of 0.5:1.

EMMPLE IV Melt a solid petroleum pitch obtained from the deep vacuum reduction of an asphaltic crude. This pitch has a softening point of 347 F. and a vanadium content of 578 parts per million. While the pitch is in molten form, add and uniformly blend therein 2.1 percent by weight of manganese oleate and 0.435 percent by weight of a sodium tallate concentrate in naphtha containing 6 percent by weight of sodium. Upon cooling and solidification, grind the mixture to about 150 mesh. The resulting fuel has an atom weight ratio of manganese to vanadium of 6. 3:1 and an atom weight ratio of sodium to vanadium of 1:1.

In order to test the efiectiveness of the additives of this invention under conditions of burning residual fuels in a gas turbine, the apparatus shown in FIGURE 1 is employed. As shown therein, the residual oil under test is introduced through line 10 into a heating coil 11 disposed in a tank of water 12 maintained at such temperature that the incoming fuel is preheated to a temperature of appriximately 212 F. From the heating coil 11 the preheated oil is passed into an atomizing head designated generally as 13. The preheated oil passes through a passageway 14 into a nozzle 15 which consists of a #26 hypodermic needle of approximately 0.008 inch ID. and 0.018 inch OD. The tip of the nozzle is ground square and allowed to project slightly through an orifice 16 of approximately 0.020 inch diameter. The orifice is supplied with 65 p.s.i.g. air for atomization of the fuel into the combustion chamber 21. The air is introduced through line 17, preheat coil 18 in tank 12, and air passageways 19 and 20 in the atomizing head 13. The combustion chamber 21 is made up of two concentric cylinders 22 and 23, respectively, welded to two end plates 24 and 25. Cylinder 22 has a diameter of 2 inches and cylinder 23 has a diameter of 3 inches; the length of the cylinders between the end plates is 8 /2 inches. End plate 24 has a central opening 26 into which the atomizing head is inserted. End plate 25 has a one (1) inch opening 27 covered by a bafile plate 28 mounted in front of it to prevent direct blast of flame on the test specimen 29. Opening 27 in end plate 25 discharges into a smaller cylinder 30 having a diameter of 1 /2 inches and a length of 6 inches. The specimen 29 is mounted near the downstream end of the cylinder approximately 1% inches from the outlet thereof. Combustion air is introduced by means of air inlet 31 into the annulus between cylinders 22 and 23, thereby preheating the combustion air, and then through three pairs of 7 inch tangential air inlets 32 in the inner cylinder 22. The first pair of air inlets is spaced inch from end plate 24; the second pair inch from the first; and the third 3 inches from the second. The additional heating required to bring the combustion products to test temperature is supplied by an electric heating coil 33 surrounding the outer cylinder 23. The entire combustion assembly is surrounded by suitable insulation 34. The test specimen 29 is a metal disc one inch in diameter by 0.125 inch thick, with a hole in-the center by means of which the specimen is attached to a tube 35 containing thermocouples. The specimen and tube assembly are mounted on a suitable stand 36.

In conducting a test in the above-described apparatus, a weighed metal specimen is exposed to the combustion products of a residual fuel oil, the specimen being maintained at a selected test temperature of, for example, 1350, 1450 or 1550" F. by the heat of the combustion products. The test is usually run for a period of hours with the rate of fuel feed being /2 pound per hour and the rate of atomizing air feed being 2 pounds per hour. The combustion air entering through air inlet 31 is fed at 25 pounds per hour. At the end of the test run the specimen is reweighed to determine the weight of deposits and is then descaled with a conventional alkaline descaling salt in molten condition at 475 C. After descaling, the specimen is dipped in 6 N hydrochloric acid containing a conventional pickling inhibitor, and is then washed, dried and weighed. The loss in weight of the specimen after descaling is the corrosion loss.

Tests are conducted in the apparatus just described using a 2520 stainless steel as the test specimen. The tests are run for 100 hours at a temperature of 1450 F. under the conditions described above. Tests are made with the fuel oil compositions of Examples I, II and III, with fuel oil compositions similar to these examples but containing different proportions of the mixture or only one of the additives in varying amounts, and with the uncompounded residual fuel oils of the examples. The following tables show the corrosion and deposits obtained.

Table l Corrosion, Wt. Loss of Deposits,

Specimen, Mg./Sq. In. Mg./Sq. I11

Uncompounded Fuel of Example I 992 319 Uncompounded Fuel of Examples II and III 1,143 231 Table II SODIUM ADDITIVES Atom Corrosion,

Wt. Wt. Loss of Deposits, Ratio, Specimen, Mg./Sq. In. Na:V MgJSq. In.

Fuel+Sodium Naphthenate. 0. 5:1 426 512 Do 1:1 110 237 Fuel Sodium Carbonate"..- 1:1 133 234 Fuel Sodium Naphthenate... 2:1 112 195 Fuel Sodium Carbonate-.. 2:1 117 211 Fuel Sodium Naphthenate-.. 3:1 96 121 D 4:1 99 370 Fuel Sodium Carbonate 5:1 91 205 Fuel Sodium Naphthenate. 6:1 34 68 Table III MANGANESE ADDITIVES Atom Corrosion,

Wt. Wt. Loss of Deposits, Ratio, Specimen, MgJSq. In. Mn:V Wig/Sq. In.

Fuel Manganese Naphthenate 1:1 382 211 2:1 137 224 3:1 92 144 4:1 55 116 6:1 14 43 Table IV SODIUM AND MANGANESE COMBINATIONS Atom Wt. Ratio, Corrosion, Additive Metals: Wt. Loss of Deposits,

V Specimen, Mg./Sq. In.

Mg/Sq. 1n.

compounded Fuel of Example I {filt gg ffff 7 e5 Compounded Fuel of i i i Example II 17 91 Compounded Fuel of fi j .1

Example III j 42 191 Fuel Manganese T s ii fi iil 0 3P t (Mn:V=0.25:1) Date {(Na:V=0.25:1) 304 85 The corrosion result for each fuel shown in the above tables was plotted against the total additive content of such fuel, separate curves being obtained for the sodium additives alone, the manganese additives alone, and the combination of sodium and manganese additives. These curves are shown in FIGURE 2.

It will be seen from the data in the above tables and the curves of FIGURE 2 that, over the entire range of proportions of total additive content of from about 1 to 4 atom weights of additive metal per atom weight of vanadium, the sodium and manganese additive com binations unexpectedly reduce corrosion to a far greater extent than the same concentration of either the sodium or manganese additives alone. Furthermore, the amount of corrosion obtained with the combination of additives tends to approach minimal, substantially negligible amounts. While the results obtained for the additive combinations in amounts less than about 1 atom Weight of total additive metal per atom weight of vanadium indicate that such combinations are unexpectedly superior to the individual additives at the same concentrations, the amount of corrosion obtained with such combinations rapidly increases with decreasing additive content, as shown when the sodium and manganese additives are each employed in an amount of 0.25 atom weight per atom weight of vanadium. On the other hand, when the additive combinations are employed in total amounts exceeding about 4 atom weights per atom weight of vanadium, the amount of corrosion obtained tends to approach that of the manganese additive used alone, as shown in FIGURE 2. Within the range of l to 4 atom weights total additive content for the combinations of alkali metal and vanadium additives, best results are obtained with amounts of from 3 to 4 atom weights. Similar results to those shown for the specific additives employed in the examples are obtained when using the other manganese and alkali metal compounds disclosed.

A typical analysis of the 25-20 stainless steel employed in the testing described is shown in the following table in percent by weight:

Resort may be had to such modifications and variations as fall within the spirit of the invention and the scope of the appended claims.

We claim:

1. A fuel composition comprising a uniform blend of a major amount of a residual petroleum fuel yielding a corrosive vanadium-containing ash upon combustion, an amount of a vanadium-free manganese compound sufficient to yield from about 0.5 to 3 atom Weights of manganese per atom weight of vanadium in said fuel, and an amount of a vanadium-free alkali metal compound sufiicient to yield from about 0.5 to 3 atom weights of alkali metal per atom weight of vanadium in said fuel, the total amount of manganese and alkali metal being at least about 1 atom weight but not exceeding about 4 atom weights per atom weight of vanadium.

2. The fuel composition of claim 1, wherein the fuel is a solid residual petroleum fuel.

3. A fuel composition comprising a uniform blend of a major amount of a residual fuel oil yielding a corrosive vanadium-containing ash upon combustion, an amount of a vanadium-free manganesse compound yielding from about 0.5 to 3 atom weights of manganese per atom weight of vanadium in said fuel oil and an amount of a vanadium-free sodium compound sutficient to yield from about 0.5 to 1 atom weight of sodium per atom weight of vanadium in said fuel oil, the total amount of manganese and sodium being at least about 1 atom weight but not exceeding about 4 atom weights per atom weight of vanadium.

4. The fuel composition of claim 3, wherein the total amount of manganese and sodium is in the range of 3 to 4 atom weights per atom weight of vanadium.

5. The fuel composition of claim 3, wherein the manganese compound is manganese naphthenate and the sodium compound is sodium naphthenate.

6. In a gas turbine plant in which a fuel oil containing vanadium is burned and which includes heat resisting metallic parts exposed to hot combustion gases and liable to be corroded by the corrosive vanadium-containing ash resulting from the combustion of said oil, the method of reducing said corrosion which comprises introducing into said plant upstream of said parts a small amount of a vanadium-free manganese compound and a vanadiumfree alkali metal compound, the amount of said manganese compound being suflicient to yield from about 0.5 to 3 atom weights of manganese per atom weight of vanadium in said fuel, and the amount of alkali metal compound being sufiicient :to yield from about 0.5 to 3 atom weights of alkali metal per atom weight of vanadium in said fuel, the total amount of manganesse and alkali metal being at least about 1 atom weight but not exceeding about 4 atom weights per atom weight of vanadium.

7. The method of claim 6, wherein the alkali metal compound is a sodium compound.

References Cited in the file of this patent UNITED STATES PATENTS Rocchini et a1 Aug. 16, 1960 FOREIGN PATENTS Great Britain Nov. 16, 1953 Great Britain Aug. 21, 1957 France Nov. 23, 1955 France Mar. 5, 1956 

6. IN A GAS TURBIN PLANT IN WHICH A FUEL OIL CONTAINING VANADIUM IS BURNED AND WHICH INCLUDES HEAT RESISTING METALLIC PARTS EXPOSED TO HOT COMBUSTION GASES AND LIABLE TO BE CORRODED BY THE CORROSIVE VANADIUM-CONTAINING ASH RESULTING FROM THE COMBUSTION OF SAID OIL, THE METHOD OF REDUCING SAID CORRSION WHICH COMPRISES INTRODUCING INTO SAID PLANT UPSTRAM OF SAID PARTS A SMALL AMOUNT OF A VANADIUM-FREE MANGANESE COMPOUND AND A VANADIUMFREE ALKALI METAL COMPOUND, THE AMOUNT OF SAID MANGANESE COMPOUND BEING SUFFICIENT TO YIELD FROM ABOUT 0.5 TO 3 ATOM WEIGHT OF MAGANESE PER ATOM WEIGHT OF VANADIUM IN SAID FUEL, AND THE AMOUNT OF ALKALI METAL COMPOUND BEING SUFFICIENT TO YIELD FROM AGOUT 0.5 TO 3 ATOM WEIGHTS OF ALKALI METAL PER ATOM WEIGHT OF VANADIUM IN SAID FUEL. THE TOTAL AMOUNT OF MANGANESE AND ALKALI METAL BEING AT LEAST ABOUT 1 ATOM WEIGHT BUT NOT EXCEEDING ABOUT 4 ATOM WEIGHT PER ATOM OF VANADIUM. 